Variable resistor



April 11, 1944. G, J MUCHER 2,346,598

VARIABLE RESISTOR:

Filed Nov. 8, 1941 INVENTOR u ATTORNEYS Patented Apr. 11, 1944 icsVARIABLE RESISTOR George J. Mucher, Brooklyn, N. Y., assigner toClarostat Manufacturing Co. Inc., Brooklyn, N. Y.; a corporation or NewYork Application November s, 1941, sensi Ns. 418,394

(or. coi-e) 9 Claims.

' This-invention relates to a new and improved electrical resistor orthe like. l

one major difficulty experienced with apparatus of this character isthat arcing of the movable member while in use causes damage to theresist' ance winding and ultimate destruction of the resistor. v

It is an object of this invention to provide. a structure of this typein which the tendency of the contact shoe to arc when in motion acrossthe winding of the resistor has been reduced to a minimum. Y

Another object is that of providing a device which is relatively'simplein construction and which will'function for long periods of time withfreedom from mechanical or electrical difficulties or failures.

With these and other objects in mind, reference is had to the attachedsheet of drawings, in which:

Fig. 1 is a plan view of one form of electrical.

resistor embodying my invention;

Fig. 2 is a cross section of the resistor shown in Fig. 1 taken alongthe lines 2-2 and looking in the direction of the arrows;

Fig. 3 is a plan view of the reverse side of the resistor shownlin Fig.1;

Fig. 4 is a side elevation partially in cross section showing theresistor illustrated in the preceding views;

Fig. 5 is a detail of the view shown in Fig. 4

circuit. The central portion of the base a is provided with a relativelylarge central opening l5 in which is disposed, for example, a collectorring i6 of metal or other electrical conductor which is substantiallythe diameter of said opening l5. Said collector ring may be, in turn,provided with a contact lead i'i extending, for example, through a sloti8 in the base 8 to a position between contacts i3 and i4. Thiscollector ring may, as has been illustrated, be formed with an outwardlyextending semi-circular iiange portion i9 which rests against the rearface of the base 8. Disposed within said collector 'ring and centrallythereof, is a shaft which rotates in a bushing 2i carried by a centralopening 22 in the other face of the base 8. Nut members 23 and 24 engagethe threaded outer surface of the bushing 2l and rest against theopposite sides oi the opening 22 thus positioning the bushing againstdisplacement. A key member 20a engages a slot in the shaft to justbeyond the outer end of the bushing 2l preventing a withdrawal of theshaft from the rear. In addition, a plate 25 of metal or other suitablematerial may be located beneath the nut 2l on the front face of the base8 and in contact therewith, said face being provided with indentures,apertures or recesses as at 26 which in turn cooperate with struck-in orbeaded portions 21 of said plate, thus keying the plate to the face ofsaid base and preventing relative rotation of the parts.

taken along the line 5-5 looking in the direction of the arrows in thatview;

Fig. 6 is a plan view of a slightly modified form of my invention; and

Fig. r1 is a plan view of still a further modification thereof.

Turning now to Figs. 1 through 5, we find an electrical resistor, forexample, a rheostat which.

is provided with a conventional base 8 formed, for example, of a ceramicor other dielectric material and in which is embedded a core or resist-vance winding 9. The latter is preferably wound on a flat metal strip I0which in turn, has been insulated by means of an inorganic insulatingmember suchas asbestos or the like i I, and after the memberhas beenwound with resistance wire, it is bent to assume the arcuate shape asshown in Fig. 1 and then placedin the slot i2 provided for that purposein the base 8. If desired, the resistance may be held in position insaid slot by any suitable cement or other adhesive. Lead members I3 andI4 are preferably secured to the opposite ends of said resistancewinding, and

In addition, a lug or abutment 28 may be carried by said platefor'cooperation with a mounting member designed to carry said resistorso that a rotation of the shaft 20, when the resistor is used, will notresult in a rotation of the entire resistor. The shaft 20 carries at itsinner end, a plate 2 9 which, as has been illustrated, may take the formof a triangle. This plate in turn, keys into an insulated actuatingcollar 30 surrounding said shaft and which may be formed of plastic,ceramic, or other insulating material. The collar may have a shoulderportion 3l adjacent its end and against which a coil spring 32 abuts.This coil spring encircles said collar as well as an insulatingauxiliary collar 33 positioned below the main collar. It might be wellat this point to draw attention to the fact that the collar 3l may justas well be -made as part of the collar 30 and if so made, would stillfunction as intended in this embodiment of my invention. The springrests at its other end against a shoulder 34 of a metallic spider orspanning member which as has been shown. may comare in turn, connectedto any desired electrical prise three leg portions, 35, 38 and 31. Thelower positioning a contact shoe This shoe as has been illustrated,bridges the gap between the col- A lector ring and the resistancewindings and is in contact with both oi there so that an electriccurrent is caused to non through the Contact shoe iront the collectorring to the resistance. A bridging member dll carried by the leg Bl,may, for esempio, cooperate with a groove ill in the upper surface oithe contact shoe and thus hold the latter member accidentaldisplacement. i lug entends inwardly from the Bange be of the spidercooperates with a stop i3 extendoutwardly from the opening l of the baseto the rotation of the spider to slightly less than ist? in eitherdirection.

li desired, and es has been shown in Fig. 6, a modined collector dd maybe used and one of the leg members l5 may be rounded so as to coopcratewith a slot do in the collector ring. n Accordingly, and whenthe spideris rotated, the leg l5 will drop into the' slot lo causing the latter toact' as e, detent to indicate to the user of the rheostat that a deniteposition, for example, the ofiposition oil the resistor has beenreached. The leg dl and the contact shoe de, as will be seen, are bothwide enough to bridge the slot lo Without any difficulty or hiterferenceso that it is only when the leg 35 reaches the slot ld that the detentaction occurs. In this connection, it will be noted that the windings lemay be so positioned that a dead space till is provided for the contactshoe, and the latter may assume a position above such dead space at thetime that the leg le rides into the detent thus eiecting anoil-position.

In Fig. 'l a further modification is shown in which individual contactpoints l are provided `in an insulated base E52 and which areprogressively spanned by the contact shoe 53 which in turn rides on thecollector ring be. In this embodiment only two legs have been shown, theone being semi-circular in cross section to cooperate with a pluralityof slots Se in the collector nog. 'reuse detest action of Lthe leg escooperating with each of the slots 5e is such that the operator can tellwhen the contact shoe b3 is in contact with each of the contact points5l. Also, as has been shown in this embodiment, the end piece 5l carriedby the shaft 5e and which cooperates with the insulating collar 59, mayhave irregular contour other than that shown in the preceding views.

in operation, it will be noted that in any of the devices described, thecontact shoe will be at all times in rm spring pressed contact with boththe collector ring and the resistance windings.

' Shock and strain imposed on the manipulating end of the shaft byeither vertical or lateral thrusts, will in each instance be absorbed bythe spider spring assembly and not transmitted through to the point ofelectrical contact. The likelihood of arcing is thus materially reduced,if not completely removed.

It is, of course, apparent that many changes might be made in theresistor construction before described and that many oi the parts mightbe rearranged without in the least departing from the spirit oi theinvention. It is also apparent that details oi design and choice ofmaterials may accesos vary over wide ranges in accordance with thespecinc needs oi the particular device under construction.

I claim:

1. An article of the character described, including in combination, abase formed of non-conducting material, a circular .resistance elementembedded in said base so that one edge thereof is exposed, said elementbeing adapted to be coupled to an electric circuit, a collector ringconcentrically disposed with respect to said resistance element andbeing also mounted on said base, said collector ring being also coupledto said electric circuit, a rotatable shaft mounted by said base, oneend thereof being positioned within said collector ring, a collectormember encircling said shaft and being coupled thereto, a plurality ofbearing legs carried by said collector member and engaging the outersurface of said collector ring, and a contact shoe coupled to one ofsaid bearing legs and making electrical contact between said collectorring and said resistance element, whereby rotation oi said shalt willcause said contact shoe to progressively engage difrerent portions ofsaid resistance element and said collector ring.

2. A resistor including in combination, a base formed of non-conductingmaterial, a circular resistance element embedded in said-base so thatone edge thereof is exposed, said element being ladapted to be coupledto an electric circuit, a collector ring concentrically disposed withrespect to said resistance element and being also mounted on said base,said collector ring being also coupled to said electric circuit, arotatable shaft mounted by said base, one end thereof being positionedwithin said collector ring, a collector member encircling said shaft andbeing coupled thereto, a plurality of bearing legs carried by saidcollector member and engaging the outer surface of said collector ring,a contact shoe coupled to one of said bearing legs and making electricalcontact between said collector ring and said resistance element, wherebyrotation of said shaft will cause said contact shoe to progressivelyengage dierent portions of said resistance element and said collectorring, and cooperating means carried by said shaft and said base forlimiting the rotation of the former with respect to the latter.

3. A resistor including in combination, a base formed of non-conductingmaterial, a circular resistance element embedded in said base so thatone edge thereof 'is exposed, said element being adapted to be coupledto an electric circuit, a co1- lector ring concentricaliy disposedwithvrespect to said resistance element and being also mounted on saidbase, said collector ring being also coupled to said electric circuit, arotatable shaft mounted by said base, one end thereof being positionedwithin said collector ring, a collector member encircling said shaft andbeing coupled thereto, a

-plurality of bearing legs carried by said collector member and engagingthe outer surface of said collector ring, a contact shoe coupled to oneof portions of said resistance element and said collector ring, and saidcollector ring being formed with a detent engageable by one of saidbearing legs to retard further movement of the latter and to indicatethat a predetermined position in the rotation of said shaft has beenachieved.`

4.. A resistor including in combination, a base formed ci non-conductingmaterial, a circular resistance element embedded in said base so thatone edge thereof is exposed, said element being adapted to be coupled toan electric circuit, a collector ring concentrically disposed withrespectt o said resistance element and being also mounted on said base,said collector ring being also coupled to said electric circuit, arotatable shaft mounted by said base, one end thereof being positionedwithin said collector ring, an insulated member carried by said shaft atthe end thereof which 'is positioned within said collector ring, acollector member encircling said insulating member and being keyedthereto, a plurality of bearing legs carried by said collector memberand engaging the outer surface of said collector ring, a contact shoecoupled to one of said bearing legs and making electrical contactbetween said collector ring.

and said resistance element, whereby rotation of said shaft will causesaid contact shoe to progressively engage different portions of saidresistance element and said collector ring, and said collector ringbeing formed with a detent engageable by one of said bearing legsto'retard further movement of the latter and to indicate that apredetermined Yposition in the rotation of said shaft has been achieved.

'5. A resistor including in combination, a base formed of non-conductingmaterial, a circular resistance element embedded in said base so thatone edge thereof is exposed, said element being adapted to be coupled toan electric circuit, a collector ring concentrically disposed withrespect lto said resistance element and being also mounted on said base,said collector ring being also coupled to said electric circuit, arotatable shaft mounted .by said base, one end thereof being positionedwithin said collector ring, an in-` sulated member carried by said shaftat the end thereof which is positioned within said collector ring, acollector member encircling said insulating member and being keyedthereto, resilient means interposed between said collector member andsaid insulating-member, a plurality of bearing legs carried by saidycollector member and engaging the outer surface of said collector ring,a contact shoe coupled to one -of said bearing legs and makingelectrical contact between said formedof non-conducting material, a.circular resistance 'element carried by said base and adapted to becoupled to an electric circuit, a collector ring concentrically disposedwith respect to said resistance element and also carried by said base,said collector ring also being coupled collector ring and saidresistance element, whereby rotation of said shaft will cause saidcontact shoe to progressively engage different portions of saidresistance element and said collector ring, and said collector ringbeing formed with a detent engageabie by one vof said bearing legs toretard further movement of the latter and to indicate thatapre-determined position in the rotation of said shaft has beenachieved.

n.6. A resistor including infconrbination, a base formed ofnon-conducting material, -acircular resistance element carried by saidbase ,and adapted to be coupled to an electric circuit, a collector ringconcentricaliy disposed with respect to said resistance element and alsocar-- to said electric circuit and a bridging contact member for makingelectrical connection between said collector ring and said resistanceelement, a rotatable shaft mounted on said base and extending throughthe same to a position within said collector ring, an insulating memberencircling said shaft and being keyed thereto for rotation therewith, aspider in turn encircling said insulating' member and being spaced fromsaid shaft by the latter, leg members carried by said spider and bearingagainst said collector ring, a leg member of said spider having yokemeans for engaging said bridging contact mem' ber and causing the sameto travel over the re sistance element and collector ring duringrotation of said shaft, and coil spring means interposed between saidinsulating member carried by said shaft and said spider for permittingrelative resilient movement between the parts as said shaft is rotated.

8. A resistor including in combination a base of non-conducting materialformed with an opening, a resistance element carried on said base, acollector ring also carried on said base,

a rotatable shaft mounted in said opening and provided with an insulatedactuating collar at one end thereof, contact shoe mounting meansencircling said shaft and in engagement with said actuating collar, saidmeans provided with aplurality of bearing legs, a surface on said basefor slidably engaging said legs, a contact shoe mounted on said meansand engaging said resistance element and collector ring, a springencircling said shaft and positioned between said shoe mounting meansand said rotatable shaft actuating collar, means for holding said shiftin position compressed against said spring thereby providing for springpressed contact between said contact shoe and said resistance andcollector ring.

'9. A resistor including in combination a base of non-conductingmaterial formed with an opening, a resistance element carried on saidbase, a collector ring also carried on said base, a

, rotatable shaft mounted in said opening and proried by said base, saidcollector ring also being coupled .to said electric circuit and abridging contactihember for making electrical connection-betweensaidcollectorringandsaidresistance element. a rotatable shaftmounted on said base and'extendingthroughthesametoaposition within saidcollector.. tins. aninsulating member said shaft and being keyed theretofor rotation therewith, a spider in turn encircling said insulatingmember andbeing spaced from said shaft by the latter, mid spider. andbearing againstsaid les members carried by collector vvided with aninsulated actuating collar at one end thereof and in axial slidingcnsmment vfixed against rotation on said shaft, contact shoe mountingmeans encircling said shaft and in axial sliding engagement with saidactuating col'- lar, said means provided with a plurality of bearinglegs, a surface on said base for slidably encasing saidlegs, acontactshoe mounted on said means and engaging said resistance elemcns andcoilectorring, aspringencirclingsaidshaftsnd positioned between saidshoe mounting means and said actuating collar, means -for holding saidshaft in position with said'spring compressed thereby providing. forspring pressed contact between said contact shoe and said resistance andcollector ring.

- GEORGE J. HUCEER.

